good power supply and well matched components.
Then the servo is unnecessary. I generally do not
use the servo, in the latest iteration, the dc output
level measured from output + to output - is about
6 millivolts. This thing will now put out 10 volts
rms into 30 ohms.

I must say Kevin i like your Style If not maby all your methods like i am not to fond of servos but you implimented the servo in the best place possible Changing the Ref voltage to the Diff amps Current sources. and while i am not to fond of bridge amps except to drive loudspeakers from low voltages. Like My portable IC Power opamp based Amp with 40 Watts rms per channel @ 4 ohms and 20 Watts @ 8 ohms. Works great for it's intended application but for headphones maby i am old fastioned but i like my headphone cords on one side, Morover who needs 10 volts into a headphone Please dont tempt Mr Apaheared, I think he is halfway so far with 6 volts and 150 MA.

The nice thing about a full H bridge implementation like this
is that the total harmonic distortion due to slight variations
between the pnp and npn output transistors is reduced to
near zero because there is always a pnp and a npn in series
for each part of the voltage swing.

I agree that the 10 volts output can make your ears bleed
but the headroom for music peaks is really nice.

And of course the main thing is that it really DOES sound
better. I've never heard any other amp that can do the
bass snap that this amp can.

Yup one thing that more available output voltage gives is more punch because of the High Headroom this is why High power amps sound Better to me anyway than low powered ones. The Bridge configuation gives twice the Slew rate Lower evean order harmonics if well matched.
ON the Down side output impedance is Twice of what eather used as a Grounded load. This can place resirictions on the lowest drivable load. but with all those output transistors i gess that is not a problem. Any how one again Nice Toutch. Just my 2C worth.

Very interesting...

Hi Kevin. Although I don't know much about amplifier design, I am intrigued by the idea of building my own HP amp. This sounds like a design that could power the AKG K1000 phones. What kind of current output is it capable of? I think that I need about 90ma into 120 ohms to get the 1 watt that those things can drink. (11 volts I think, but I am doing this from some very hazy memories, which is risky).

btw, my HD600s were already "dual mono" in that they have a separate ground on each side. My brand new 600s had a bad mini-plug (I hate mini-plugs!) so I clipped it off and added a 1/4" plug. Each of those 2 sides carry a + and a -, and the R & L can be split apart. Very small gauge with micro-insulation and kevlar core, so a bit difficult to work with, but workable. The insulation flames right off with a torch lighter. I don't know if the earlier units have the same type of cables as mine. Mine have a distinct joined double cable (like zip cord).

Incidentally, anybody know of a source for the plugs that go into the cans of the HD600s? I want to build my own cables.

>>What kind of current output is it capable of? I think that I need about 90ma into 120 ohms to get the 1 watt that those things

The amp will fall out of pure class A, but will definitely
deliver this amount of current and more.

Let me just point out that if the akg headphones are even
25% efficient, this is 250 milliwatts of audio power which
can and will do serious hearing damage. But it will sound
really nice while its destroying your hearing...